Question

The heart cannot convert lactate back to glucose, as the liver does, but instead uses it as a fuel. What is the ATP yield from the complete catabolism of one mole of lactate?

Short answer

18 ATPs are obtained from the complete catabolism of one mole of lactate.

Step-by-step solution

 Sources of energy for heart cells

Fatty acids, ketone bodies, glucose, pyruvate, and lactate are all sources of energy for heart cells. Lactate can be used as a key energy source by cardiac cells during exercise.

Lactate catabolism

The conversion of lactate to pyruvate is the first step in lactate catabolism, where one NADH molecule is produced. The pyruvate is then transformed to acetyl-CoA, resulting in the formation of another NADH molecule.

Acetyl-CoA then enters the Krebs cycle. The Krebs cycle generates one ATP molecule, three NADH molecules, and one FADH₂ molecule.

Result of Lactate catabolism

Lactate metabolism generates 5 NADH, 1 ATP, and 1 FADH₂.

Each NADH molecule generates 3 ATP.

FADH₂ generates two ATP molecules.

In total, 18 ATP are produced

Therefore, for every mole of lactate, 18 ATP molecules are created.